Electric heaters for water tanks are well known in the art and generally comprise a metal sheathed heater of hairpin formation with a metal mounting member connected across the two legs of the sheath. The mounting member was either a plate which was bolted to the tank wall, or a screw plug which was threaded into a fitting on the tank wall. At the present time, the manufacturers of water tanks prefer the screw-plug type of mounting member. Metal screw plugs heretofore used are relatively costly to produce, and they tend to corrode after a period of use and then are difficult to remove from the tank.
Screw plugs formed of a plastic material have many advantages over the metal plug since they are less costly to produce and are free of corrosive problems. However, since such plugs tend to electrically isolate the heating element from the water tank, a grounding member must be incorporated; otherwise, corrosive erosion of the sheath will occur after a period of use.
The mounting structure disclosed in the said Jacobs patent eliminated the disadvantages of the metal screw plug and provided an efficient mounting member that was well received in the trade. However, because the grounding member in the Jacobs structure was assembled with the legs of the heater before molding, the mold cavity had to be contoured to accomodate the grounding member and this insert molding increased cost.
My invention retains the many advantages of the Jacobs structure but eliminates the need for a costly mold. A plastic plug is molded in a simple mold and then assembled with the legs of the heating element with a force fit. A grounding member in the form of a metal strip of U-shaped formation has its bight portion mechanically and electrically connected to the heating element legs, and the terminal portion of its legs adapted to engage the ring welded to the tank wall around the opening in the wall. A flange-type mounting plate may be used instead of the screw plug type mounting.
The heating element herein disclosed may be adapted to provide a controlled amount of galvanic current flow between the sheath of the heating element and the wall of the hot water tank, as disclosed in U.S. Pat. No. 2,723,340, issued Nov. 8, 1955, to A. C. Boggs et al., and in U.S. Pat. No. 2,810,815, issued Oct. 22, 1957, to H. C. Dicome, both of these patents being assigned to the assignee of the present application.